A mobile unit (MU) may be configured with a transceiver to communicate with a network. The transceiver is coupled to a main antenna such that the transceiver is capable of connecting to the network on a particular operating frequency of the network. Accordingly, the main antenna is designed to transmit/receive signals from the transceiver to the network on the operating frequency. For example, a cellular network which is based upon a Global System for Mobiles (GSM) network is utilizing a high-band frequency of 1900 MHz. In another example, a cellular network which is based upon a Code Division Multiple Access (CDMA) network is utilizing a high-band frequency of 1800 MHz. In yet another example, a low-band frequency ranging between 800-900 MHz may also be used such as in cellular networks. Therefore, the antenna allows the transceiver to operate on these frequencies.
A conventional MU may include a respective main antenna for each operating frequency, thereby enabling the transceiver to transmit/receive signals in different networks. That is, the MU may include a first main antenna to operate in the GSM network, a second main antenna to operate in the CDMA network, and a third main antenna to operate in the cellular network. However, this requires multiple main antennas to be disposed within the housing of the MU, each main antenna requiring respective connections/components.
In certain environments such as urban or indoor environments, there is no clear line-of-sight (LOS) between a transmitter and a receiver of the wireless link. Accordingly, the signal is transmitted from the transmitter to be reflected along multiple paths before finally being received by the receiver. Each of these bounces introduces phase shifts, time delays, attenuations, and distortions that can destructively interfere with one another at the aperture of the receiving antenna. Therefore, the conventional MU may further utilize different types of antenna arrangements that enable the transceiver to operate on the above described frequencies. Specifically, an antenna diversity scheme may be used. The antenna diversity scheme relates to the use of two or more antennas to improve the quality and reliability of a wireless link. For example, the antenna diversity scheme may relate to a spatial diversity, a pattern diversity, a polarization diversity, a transmit/receive diversity, adaptive arrays, etc. in which multiple antennas are utilized. Antenna diversity is especially effective at mitigating the above-described multipath situations because multiple antennas offer a receiver several observations of the same signal. Each antenna experiences a different interference environment. Thus, if one antenna is experiencing a deep fade, it is likely that another has a sufficient signal. Collectively such a system provides a robust link.
Inherently, the antenna diversity scheme requires additional hardware and integration versus a single antenna system. Specifically, the conventional MU utilizing the antenna diversity scheme may include the main antenna configured to both transmit and receive data and a diversity antenna which is conventionally configured to only receive data. Furthermore, with the multiple signals, there is a greater processing demand placed on the receiver which leads to tighter design requirements. However, due to the commonality of the signal paths, a fair amount of circuitry may be shared between the main antenna and the diversity antenna. In addition, signal reliability is paramount and using multiple antennas is an effective way to decrease the number of drop-outs and lost connections.
In a substantially similar manner as the main antenna, the diversity antenna should also be configured to operate in the same frequencies that the main antenna is configured to operate. Accordingly, a conventional diversity antenna may include substantially similar drawbacks. For example, to operate in a first operating frequency that the main antenna is configured to operate, the conventional MU may include a first diversity antenna; to operate in a second operating frequency that the main antenna is configured to operate, the conventional MU may include a second diversity antenna; etc. Therefore, this requires multiple diversity antennas as well to be disposed within the housing of the MU, each diversity antenna requiring respective connections/components. Furthermore, the diversity antenna is a supplemental antenna used in the antenna system of the MU. As such, the diversity antenna is often subject to more constrained physical parameters as less space is available to include this supplemental antenna. Accordingly, the diversity antenna is usually configured for only select ones of the operating frequencies of the main antenna. For example, if the main antenna is configured for four different operating frequencies, the diversity antenna is often configured for only two of the four different operating frequencies (e.g., the two most commonly used among the four).
Accordingly, there is a need for a combined diversity antenna that is capable of operating in multiple frequencies such as two low band frequencies and two high band frequencies so that the combined diversity antenna is capable of being used in global applications.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.